Use of a brush to clean teeth is a generally accepted means of maintaining oral hygiene. Consequently, many different styles and types of toothbrushes are either disclosed in the art or available in the market. Different combinations of bristle stiffness, handle design, brush head profile, bristle contour and the like provide varying degrees of cleaning, comfort, and, unfortunately, tooth and gum tissue damage.
It is generally known that toothbrushes with contoured bristle heights, such as a sinusoidal wave form, enable the bristles to more easily penetrate the space between the teeth, thereby providing improved cleaning.
It is also generally known that end rounding of individual bristles reduces tooth and gum tissue damage by removing the sharp edges which result from the bristle trimming operation. Positioning the free ends of the bristles against an orbital grinder is a very effective means to achieve end rounding when the free ends of the bristles terminate within a common plane. However, with a contoured brush insufficient penetration of the grinder into the bristle tufts tends to round only the longest bristles. Conversely, grinder penetration sufficient to end round the shorter bristles damages and distorts the longer bristles.
Complex grinding systems have been developed to attempt to end round bristles after they have been attached to the brush head and trimmed to the desired contour. For example, U.S. Pat. No. 2,227,126 issued to Cooke on Dec. 31, 1940 discloses a complex combination of contoured grinding wheels, blades, and oscillating motions used in an attempt to end round the tips of bristles which are not within a common plane. The disclosed process is expensive, marginally effective, and limited to relatively simple contours.
U.S. Pat. No. 2,426,328 issued to Wandel et al. on Aug. 26, 1947 discloses a thermal process for end rounding bristles. However, the thermal process, especially for a contoured brush pattern, is a very random process. Thickening of the bristle ends or fusion of the bristle ends to one another typically results. Both of these characteristics are undesirable in the finished toothbrush. Means to remove such thickenings or fusions, such as with a steel brush, are disclosed. However, such removal techniques tend to produce bristle tufts wherein the tips of the individual bristles are no longer uniformly end rounded.
U.S. Pat. No. 4,979,782 issued to Weihrauch on Dec. 25, 1990 discloses a process for producing a contoured brush having individual bristle ends that are substantially uniformly rounded and located in a contour differing from that of the bristle carrier. This is accomplished by a bristle tuft clamp system. The disclosed process includes the steps of: clamping the bristles while the utilization-side ends are in a flat plane; substantially uniformly rounding the utilization-side ends of the bristles while they are clamped in the flat plane; loosening the clamp restraining the bristles; axially displacing the utilization-side ends of the bristles relative to one another to produce the desired contour; and thereafter fastening the opposite ends of the bristles to the bristle carrier. Although sophisticated manufacturing systems of the type generally disclosed in U.S. Pat. No. 4,979,782 permit three-dimensional profiling of individual bristle tufts as well as three-dimensional profiling of the bristle tufts relative to one another, they differ markedly from most commercially available toothbrush production systems. In addition they require operating personnel having a high level of technical competence.